In a bogie suspension, flexibility in the vertical direction between the bogie chassis and each axle box must be provided. It is also necessary for each axle box to be guided with respect to the chassis, longitudinally and transversely.
Various types of bogie are known in which elastic studs are mounted between the bogie frame and each axle box.
In certain bogies, the suspension and coupling between the frame and each axle box are formed solely by means of studs of elastomer framing this axle box. Each elastic stud is housed between two parallel support surfaces slightly inclined with respect to the vertical. The studs are positioned in pairs in dihedra whose bisector planes are vertical, this arrangement enabling a vertical load of combined compressive and shearing stresses to be supported. The rigidity in the vertical direction is not negligable.
In other bogies, helicoidal springs for ensuring the vertical suspension are associated with studs of elastomer providing the flexible couplings. In certain bogies each elastomer stud is housed between two parallel support surfaces slightly inclined with respect to the vertical. These flexible studs are positioned in pairs in dihedra of which the bisector planes are vertical so that the vertical loads are supported with combined compressive and shearing stresses. The elastomer studs are mounted in parallel with the vertical suspension springs. This arrangement disturbs operation particularly with high frequency stresses.
In other bogies the suspension and coupling between the chassis and the axle box are formed by a helicoidal spring and elastic studs which frame the axle box. Each elastic stud is housed between two vertical support surfaces and the elastomer material is prestressed by squeezing. Under the effect of creep the prestressing diminishes in time.